The Bush administration already has its fair share of controversies, national and international, with which to contend. But now one more can be added to the list: the growing dispute over the annual White House Easter Egg Roll.

Some religious conservatives have objected to plans by several hundred gay and lesbian parents to attend the historic celebration on Monday on the south lawn of the presidential home, accusing them of "crashing" the event and politicising a 130-year-old tradition.

"The Easter Egg Roll has remained non-controversial for too long, apparently," Mark Tooley, of the conservative Institute on Religion and Democracy, wrote in the Weekly Standard magazine. He said one of the organising groups, Soulforce, was "well-known for its disruptive demonstrations and acts of civil disobedience at the conventions of religious denominations that do not share its views on sexual ethics".

The event is open to the public, and the White House has remained tight-lipped on the attendance of gay parents. "This event is a time to celebrate Easter and to have a good family celebration," was all Scott McClellan, the president's spokesman, would say when asked. The first family may be split on the issue: George Bush has made clear his opposition to same-sex marriage, but Laura Bush, who officially hosts the event, is thought to harbour more liberal views.

One of the parents who planned to attend as a member of the gay rights group Family Pride said the goal was to reach beyond politics. "It's so funny to us that people are saying we're politicising this," Colleen Gillespie, a New York University professor, told the Guardian. "We're going so that American citizens across the country can see and meet our families, rather than hear politicians talk about us. It's only the extreme right that seem to be unable to imagine us as families. And it's a pretty neat event. The children will remember it for the rest of their lives."

The Easter Bunny is understood to be sick of getting embroiled in disputes. He was physically attacked in 2003 in a Wisconsin shopping mall - prompting local police to make an arrest - and beaten up again last year in Michigan, while posing for photographs with local children.